benabloom
Member
- Messages
- 420
Hi ,
I have a Bandmaster Reverb from '69, that has been modified with a Hoffman style turretboard and AB763 spec'ed, exceot that it has the earlier bias modulating trem (sounds great btw). Now the board was purchase stuffed from the airtightgarage and looks pretty, however I did not independantly varify the values of each component. This has been a long running project amp.
All of the Transformers are original and it is now living in a 2x10 cabinet (like a vibroluxe reverb) with 2 weber 10f150 speakers wired to = 4ohms total.
My issues with the amp as it is is that I cannot get any breakup at all even on 10. stays clean and loud. I tried biasing the tubes hotter and cooler and while the tone changes, there is no tube distortion happening.
Also of note, with a Gz34 recto I am measuring about 420v on the plates, and with a 5u4gb recto I am getting a measily 400v on the plates. Are these voltages indicative of a bad power transformer? something else on the circuitboard seem off with these readings?
I would like the amp to breakup earlier and it does not seem normal to me as it is. I am up for the challenge... now what should I do , look for etc?
-Ben
I have a Bandmaster Reverb from '69, that has been modified with a Hoffman style turretboard and AB763 spec'ed, exceot that it has the earlier bias modulating trem (sounds great btw). Now the board was purchase stuffed from the airtightgarage and looks pretty, however I did not independantly varify the values of each component. This has been a long running project amp.
All of the Transformers are original and it is now living in a 2x10 cabinet (like a vibroluxe reverb) with 2 weber 10f150 speakers wired to = 4ohms total.
My issues with the amp as it is is that I cannot get any breakup at all even on 10. stays clean and loud. I tried biasing the tubes hotter and cooler and while the tone changes, there is no tube distortion happening.
Also of note, with a Gz34 recto I am measuring about 420v on the plates, and with a 5u4gb recto I am getting a measily 400v on the plates. Are these voltages indicative of a bad power transformer? something else on the circuitboard seem off with these readings?
I would like the amp to breakup earlier and it does not seem normal to me as it is. I am up for the challenge... now what should I do , look for etc?
-Ben